Giant salvinia, also known as water fern or kariba-weed, was introduced as an ornamental aquatic plant and is spread to new water bodies on boats and fishing gear, by dumping of aquaria, and by other unintentional means. Sale, transport, release and other activities with this plant are prohibited in the United States by Federal law. It poses a serious threat to lakes, ponds, streams, rivers and other freshwater wetlands, and cultivated rice fields. Giant salvinia grows rapidly and spreads across water surfaces, forming dense floating mats that cut off light to other aquatic plants, reduce oxygen content and degrade water quality for fish and other aquatic organisms.